Processes for preparing polyamides from dicarboxylic acids and diamines or from lactams such as caprolactam are well known. The processes are typically carried out at high temperatures, if necessary under superatmospheric pressure by admixture and later removal of an aqueous phase.
There have also been reports in the past about the preparation of polymers by reaction in ionic liquids.
WO 2006/048171 relates to the preparation of polyisocyanates by reaction of primary amines with phosgene in the presence of ionic liquids as solvents. Substituted imidazolium chlorides in particular are used as solvents.
WO 02/079269 describes the polymerization of vinylic starting monomers by free radical or thermal polymerization in ionic liquids.
Y. S. Vygodskii et al., in Macromol. Rapid Commun. 2002, 23, pages 676 to 680, describe ionic liquids useful as reaction media for the synthesis of condensation polymers. Aromatic diamines are reacted with anhydrides or with acyl chlorides of di- and tetracarboxylic acids, which leads to the preparation of polyamides and polyimides. The carboxylic acids have to be present in derivatized form.
E. I. Lozinskaya et al., in European Polymer Journal 40 (2004), pages 2065 to 2075, describe the direct polycondensation in ionic liquids. Similarly, the preparation of different polyamides from dicarboxylic acids and diamines is described, although in each case a 2.25-fold molar excess of diphenyl phosphite has to be used as an activating agent.